Ultraviolet-visible fluorescence of 2p-excited argon - art. no. 062504

Ultraviolet-visible fluorescence (300 nm less than or equal to lambda less than or equal to 500 nm) of argon is investigated in the Ar 2p excitation r egime (240 eV less than or equal to E less than or equal to 260 eV) using m onochromatic synchrotron radiation for primary excitation. Fluorescence exc itation spectra and dispersed fluorescence spectra at constant photon energ y are reported as well as time-resolved dispersed fluorescence profiles. Va rious radiative processes are assigned, indicating that these processes are primarily due to the relaxation of Ari. A distinct state-selective behavio r is found for some fluorescence excitation spectra, whereas others show no state selectivity at all. Time-resolved experiments give further insight i nto this state-selectivity and excited-state lifetimes. The results indicat e that excited cation states are either directly formed as a result of prim ary Ar 2p excitation and subsequent electronic relaxation or via subsequent radiative cascades. The present results are consistent with earlier work o n resonant Auger spectroscopy, extending the dynamic range of processes occ urring in the Ar 2p regime into the nanosecond time regime.